The present invention relates to a novel and efficient, air-cooled ozone generator of tubular type.
Ozone is an allotropic modification of oxygen which is formed by the condensation of three oxygen molecules to two ozone molecules. Ozone is present in the atmosphere to a varying extent and is continuously formed in the outer layer of the atmosphere by the action of the ultraviolet rays of the sun on atmospheric oxygen. Ozone, which is a powerful oxidizer, has a disinfecting and deodorizing effect and is used, inter alia, for disinfecting water, for instance to form potable water, for treatment of industrial wastes, and for the inhibition of fungal, bacterial and viral growth in stores. Ozone can be used for these purposes with most all agricultural products.
The preparation of ozone has been known for a long time and is performed by electric discharge in a space between two electrodes. This space houses a dielectric, such as glass. The discharge space between one electrode and the dielectric in general is of the order of 2-3 mm. The discharge, which is produced by connecting the electrodes to a high-voltage AC source, is of the quiet electric discharge type or the corona or convection discharge type.
All commercial ozone generators are based on the same fundamental principle but differ in respect of component design, dimensions, cooling, electrode design, dielectric etc. Minaturized gas-cooled ozone generators are usually constructed with a single pair of plate or tubular electrodes with an intermediate plate or tubular dielectric. Of prior art ozone generators mention should be made in particular of those disclosed in the following patent specifications.
British Patent Specification No. 1,528,731 describes a tubular ozone generator of the type including an inner electrode, a coaxial outer electrode surrounding the inner electrode, and a tubular dielectric disposed between the inner and outer electrodes. Characteristic of the device of this patent specification is that the discharge space in which the ozone is produced is in the form of a helical path. In addition, the outer electrode is provided with axial cooling ribs or fins.
U.S. patent specification No. 3,214,364 relates to an improvement of the well-known Welsbach-Traligaz ozonator. The ozonator according to this patent specification has a water-cooled tubular outer electrode, a tubular inner electrode of metal, for instance a wire mesh, and a tubular dielectric, such as a glass tube, which is arranged concentrically between and spaced from the outer and inner electrodes. One end of the glass tube is provided with a plate having an orifice which restricts gas flow through the tube.
U.S. patent specification No. 1,834,705 relates to a tubular ozone generator characterized by a corrugated sheet of heat conducting metal, such as copper, which surrounds the dielectric and the outer electrode to conduct heat therefrom.
A major portion of the electric energy supplied to an ozone generator is released in the form of heat, which has an adverse effect on the ozone yield. The decomposition reaction of the ozone to form oxygen will predominate over the reverse reaction in which ozone is formed from oxygen at as low a temperature as 40.degree. C. Hence, it is of decisive importance that the ozone generator is provided with efficient cooling. The problem of obtaining efficient cooling is encountered in particular in gas-cooled ozone generators, for instance miniaturized portable ones, in which it is not possible or expedient to resort to water-cooling, oil- or other fluid-cooling. Further, efficient cooling is vital because overheating of the dielectric will considerably shorten its life. For instance, inefficient cooling may cause overheating and cracking of the dielectric, thus making the ozone generator unusable. Gas-cooling of the ozone generator allows the unit to be lighter in weight, more portable and more compact.